Sham's The Enemy Within

Skaven

A race of Chaos-tainted rat-men, rumoured to have infested many of the Old World’s caves, tunnels, mines, and sewers. There is little agreement over the extent of their presence; some doubt they exist at all, while others insist that they are literally everywhere under the surface. Saner Imperial rulers have tended to assume the skaven, if they are a true group on the own, are merely a different type of Beastmen, largely a threat in the deep wilderness.